The compound having the formula:
is known as prasugrel. Prasugrel and pharmacologically acceptable salts thereof are known to have a platelet aggregation-inhibiting action and are useful as an active ingredient of a medicine (particularly, an antithrombotic or anti-embolic agent) (JP06-41139 or JP2002-145883). However, the use of prasugrel or a pharmacologically acceptable salt thereof as a medicine has required a technique for producing the prasugrel or a pharmacologically acceptable salt thereof at a high purity.
WO96/11203 describes a method for producing prasugrel or a pharmacologically acceptable salt thereof. In addition, JP2002-145883 describes a method for producing prasugrel hydrochloride or maleate, which involves reacting an acid with free prasugrel. However, neither of these patent documents describes a method for decreasing the by-product OXTP.    Patent Document 1: JP06-41139    Patent Document 2: JP2002-145883    Patent Document 3: WO96/11203